Matrix Orbital GLK240128-25 - Manual (Page 55)

50 Command Summary
send a 128 byte block of data followed by that blocks high and low CRC16 bytes. The display then
performs a CRC check on the data receive and ACKs if it matches that which was sent. Transfer
continues with a block count and continues in this way until the end of file is reached. Files may be
padded with 255 values to reach an even multiple of 128 bytes in size, but the download command will
always report true size. Once the end of the upload file is reached, the host should transmit a single end
of transmission byte. If the end of file is expected, the display will ACK one last time.
Table 42: XModem File Upload Protocol
Host Display Comments
254 Command Prefix
220 XModem Upload Command
133 Command Byte One
6 Command Byte Two
48 Command Byte Three
1 File ID LSB
0 File ID MSB
1 File Type
0 Size LSB
0 Size
1 Size
0 Size MSB
67 C (If file fits)
1 Start of Header
128 Block Count
127 Inverted Block Count (255-Count)
<128 B> 128 Byte Data Block
30 * CRC MSB
71 * CRC LSB
6 ACK (NAK if counts don’t match)
… … …
4 End of Transmission
6 ACK (NAK if EOT is not expected)
Table 43: XModem File Download Protocol
Host Display Comments
254 Command Prefix
221 XModem Download Command
133 Command Byte One
6 Command Byte Two
48 Command Byte Three
1 File ID LSB
0 File ID MSB
1 File Type
0 Size LSB (NAK if not found)
0 Size
1 Size
0 Size MSB
67 C
1 Start of Header
128 Block Count
127 Inverted Block Count (255-Count)
<128 B> 128 Byte Data Block
30 * CRC MSB
71 * CRC LSB
6 ACK (NAK if counts don’t match)
… … …
4 End of Transmission
6 ACK (NAK if EOT is not expected)
Table 44: XModem Message Bytes
Value Action Description
1 Start of Header Begin upload transfer
4 End of Transmission End completed upload transfer
6 Acknowledged Transfer successful, upload continues
21 Not Acknowledged Transfer failed, upload aborted
67 C Confirmation that file will fit
*Note: CRC bytes are calculated using the XMODEM CRC-CCITT algorithm available at:
http://www.matrixorbital.ca/appnotes/XModem/ymodem.txt .